Avilés-Moreno Juan Ramón, Berden Giel, Oomens Jos, Martínez-Haya Bruno
Department of Physical, Chemical and Natural Systems, Universidad Pablo de Olavide, 41013, Seville, Spain.
Radboud University, Institute for Molecules and Materials FELIX Laboratory, Toernooiveld 7c, 6525ED, Nijmegen, The Netherlands.
Chemphyschem. 2018 Sep 5;19(17):2169-2175. doi: 10.1002/cphc.201800596. Epub 2018 Aug 1.
Crown ethers are well known as modulating agents of protein function and interactions. The action of crown ethers is driven by an alteration of the charged moieties of proteins through the capping of cationic amino acid side chains. This study evaluates the conformational features involved in the binding of crown ethers to the side chain of arginine. For this purpose, isolated complexes of methyl guanidinium with 12-crown-4 and 18-crown-6 are characterized with infrared action vibrational spectroscopy and quantum chemical computations. The conformational landscapes of the two complexes comprise an extensive ensemble of conformations close in energy. In the 12-crown-4 complex, the crown ether has the plane of its backbone approximately perpendicular to that of the guanidinium moiety and coordinates to two or three of its NH bonds. In the 18-crown-6 complex, the crown ether backbone is partially folded and tilted with respect to guanidinium and fixes its position in order to facilitate up to a four-fold coordination in the complex. The access of the complexes to multiple conformations leads to broad band structures in the N-H stretching region of their vibrational spectra.
冠醚作为蛋白质功能和相互作用的调节剂而广为人知。冠醚的作用是通过阳离子氨基酸侧链的封端改变蛋白质的带电部分来驱动的。本研究评估了冠醚与精氨酸侧链结合所涉及的构象特征。为此，用红外作用振动光谱和量子化学计算对甲基胍与12-冠-4和18-冠-6的分离复合物进行了表征。这两种复合物的构象景观包含大量能量相近的构象。在12-冠-4复合物中，冠醚主链平面大致垂直于胍基部分的平面，并与其两个或三个NH键配位。在18-冠-6复合物中，冠醚主链相对于胍基部分部分折叠并倾斜，并固定其位置以促进复合物中高达四重配位。复合物能够形成多种构象，导致其振动光谱的N-H伸缩区域出现宽带结构。
